Hi, i hope somebody can help. I'm renovating my victorian property and last week had the dining room electrics done. at this stage all of the walls were fine. previously due to the chimneys and air bricks being blocked the plaster on one wall had gone popcorny and we had removed it and dried out the wall. today the plasterer came to patch up the wall. a week ago he had visited to quote me so had inspected the whole room (no visable damp problem). he set up and after about an hour called me downstairs. he said i had rising damp and there was a highly visible tide mark on all three walls of the room (the forth wall is an archway leading into living room) I don't think this tide mark was there the night before and certainly wasn't the week before when he provided the quotation. I've ripped up the floorboards and there is not a leaking pipe and the brickwork and mortar under the plaster seem dry (i have removed a little to check). how can sudden extreme rising damp occur and what should i do next?

A simple test that you can carry out to see if you have damp in the walls is to get a household drill and drill into the plaster showing damp, drill straight through into the brickwork. If the drill sample comes out dusty then this means the wall is dry, if rising damp is in the brickwork then the sample will come out wet. Let me know what is? Hope this can help

a couple of hours later the wall had dried out and the tide mark gone. i took off some of the plaster and examined the bricks. they were dry and the mortar is dusty to the touch. I have a feeling that the look of damp was created by the workman by covering the finished walls with the diluted pva solution he was using to cover the bit of brickwork he was supposed to be plastering. I licked the wall (bit odd i know) and it tasted of pva glue. shame as the painted and finished walls have now been ruined as the pva has left a bit of a different finish. A neighbour took a look and said that there was no damp. all very confusing, but i think i've been nobbled!